A Study on Contact Characteristics of Metal and n-Type 4H-Silicon Carbide
| Autor: | Cheng, Jung-Chien, 鄭嶸健 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Recently, the supply and demand of power become an attractive issue. Elevating the power transfer efficiency is one of the most important factors for power saving and carbon reduction. Compared with the traditional Si-based power devices, using the wide bandgap semiconductors as the starting material can raise the blocking voltage rating and reduce the power loss during device operation. Among the wide bandgap semiconductors, 4H-SiC is generally considered as a candidate for the next-generation power device. Furthermore, the high thermal conductivity of 4H-SiC is beneficial for high-temperature and high-current applications. However, the high costs of epitaxial substrates and special fabrication processes is the bottleneck for replacement of Si-based power devices. The goal of our research is to develop a fabrication process of metal-semiconductor contact containing a controllable Schottky barrier height. Meanwhile, this fabrication process can reduce specific contact resistance of the ohmic contact according to the Schottky barrier height modulation. In this dissertation, several surface treatments applied on the n-type Schottky contact are developed, including dielectric layer insertion, Ar inductively coupled plasma treatment, and rapid thermal annealing. The Schottky barrier height can be precisely pinned at a certain level by different post-metal-deposition annealing temperatures. The device-to-device deviation can be minimized at the same time. The mechanism of Schottky barrier height modulation is studied by electrical characterization and material analyses. According to the Schottky barrier modulation, those surface treatments were applied on the ohmic contacts for the reduction of specific contact resistance. The specific contact resistance of the ICP-treated Ti ohmic contacts on room-temperature-implanted n+-SiC after 600 ℃ post-metal-deposition annealing is 8.3×10-7 Ω-cm2, which is the lowest value in this dissertation. This result suggests that the ohmic contact can be formed by room-temperature implantation, which is more economic than general high-temperature implantation. Besides, the low post-metal-deposition thermal budget results in a smoother morphology of the metal-semiconductor interface, which is beneficial for contact reliability. Based on the former study of our research group, the feasibility of LOCOSiC process with an Ar ion pre-amorphization implantation is proofed. We have verified the impact on the metal-semiconductor contact and n+/p junction diode, which are sensitive to the quality of field oxide grown by LOCOSiC process or deposited by PECVD. Compared with the PECVD-oxide-isolated diodes, the smoother edge profile and the better oxide quality of LOCOSiC isolation are beneficial for high-power electronics to suppress the leakage current and prevent immature breakdown without edge termination. However, the parameters of LOCOSiC process have to be optimized to prevent the recrystallization of pre-amorphized SiC and the unpredictable degradation. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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